Eye-fatigue examining device and eye-fatigue examining method

Abstract

An eye-fatigue examining device and an eye-fatigue examining method capable of examining eye fatigue of a subject's eye regardless of an age of a patient are provided. The eye-fatigue examining device includes: a light quantity difference adjusting unit that increases a light quantity difference between lights respectively incident on right and left subject's eyes; a gaze direction detecting unit that detects gaze directions of the respective subject's eyes while the light quantity difference adjusting unit increases the light quantity difference; and a light quantity difference deciding unit that decides a specific light quantity difference at which a change in the gaze directions due to the increase in the light quantity difference occurs, based on the detection result of the gaze direction detecting unit.

The invention claimed is: 
     
       1. An eye-fatigue examining device comprising:
 processing circuitry configured to control liquid crystal shutters to increase a light quantity difference between lights respectively incident on right and left subject's eyes; 
 the processing circuitry further configured to detect gaze directions of the respective subject's eyes while controlling the liquid crystal shutters to increase the light quantity difference; and 
 the processing circuitry further configured to decide a specific light quantity difference at which a change in the gaze directions due to an increase in the light quantity difference occurs, based on the detected gaze directions of the respective subject's eyes detected by the processing circuitry, 
 wherein the processing circuitry is further configured to output the decided specific light quantity difference as an index of eye fatigue of the subject's eyes. 
 
     
     
       2. The eye-fatigue examining device according to  claim 1 , comprising a visual target display configured to display an examination visual target to be visually observed by the subject's eyes,
 wherein the processing circuitry decides the specific light quantity difference, by determining presence or absence of a change in the gaze directions from a state in which the subject's eyes visually observe the examination visual target based on the detected gaze direction. 
 
     
     
       3. The eye-fatigue examining device according to  claim 2 ,
 wherein the processing circuitry detects positions of Purkinje images of the subject's eyes or positions of pupils of the subject's eyes, and 
 the processing circuitry decides the specific light quantity difference, by determining presence or absence of a change in the positions of the Purkinje images or the pupils from a state in which the subject's eyes visually observe the examination visual target. 
 
     
     
       4. The eye-fatigue examining device according to  claim 1 ,
 wherein the processing circuitry increases the light quantity difference, by decreasing a light quantity of a light incident on one of the subject's eyes and maintaining a light quantity of a light incident on the other of the subject's eyes constant. 
 
     
     
       5. The eye-fatigue examining device according  claim 1 ,
 wherein the liquid crystal shutters include a transmitting area which can adjust a transmittance of the light incident on at least one of the subject's eyes, and processing circuitry increases the light quantity difference by adjusting the transmittance of the transmitting area. 
 
     
     
       6. The eye-fatigue examining device according to  claim 5 ,
 wherein, when the liquid crystal shutters have the transmitting area on an optical path of the light incident on each of the subject's eyes, the specific light quantity difference decided by the processing circuitry is expressed as a difference in the transmittance between the two transmitting areas. 
 
     
     
       7. The eye-fatigue examining device according to  claim 1 ,
 wherein the processing circuitry continuously or stepwise increases the light quantity difference. 
 
     
     
       8. The eye-fatigue examining device according to  claim 1 ,
 wherein the lights incident on the subject's eyes include a light in a first wavelength band and a light in a second wavelength band different from the first wavelength band, 
 a dichroic mirror is provided on optical paths of the lights reflected by the subject's eyes, the dichroic mirror configured to transmit the light in the first wavelength band and reflect the light in the second wavelength band reflected by the subject's eyes to a side of the optical paths, and 
 the processing circuitry detects the gaze directions based on a result of detecting the light in the second wavelength band reflected by the dichroic mirror. 
 
     
     
       9. An eye-fatigue examining method comprising:
 a light quantity difference adjusting step of increasing a light quantity difference between lights respectively incident on right and left subject's eyes; 
 a gaze direction detecting step of detecting gaze directions of the respective subject's eyes while the light quantity difference is increased in the light quantity difference adjusting step; 
 a light quantity difference deciding step of deciding a specific light quantity difference at which a change in the gaze directions due to an increase in the light quantity difference occurs, based on a detection result of the gaze direction detecting step; and 
 an outputting step of outputting the specific light quantity difference decided in the light quantity difference deciding step as an index of eye fatigue of the subject's eyes. 
 
     
     
       10. The eye-fatigue examining method according to  claim 9 , comprising
 a visual target displaying step of displaying an examination visual target to be visually observed by the subject's eyes, 
 wherein in the light quantity difference deciding step, the specific light quantity difference is decided, by determining presence or absence of a change in the gaze directions from a state in which the subject's eyes visually observe the examination visual target based on the detection result in the gaze direction detecting step. 
 
     
     
       11. The eye-fatigue examining method according to  claim 10 ,
 wherein in the gaze direction detecting step, positions of Purkinje images of the subject's eyes or positions of pupils of the subject's eyes are detected, and 
 in the light quantity difference deciding step, the specific light quantity difference is decided by determining presence or absence of a change of the positions of the Purkinje images or the pupils from a state in which the subject's eyes visually observe the examination visual target. 
 
     
     
       12. The eye-fatigue examining method according to  claim 9 ,
 wherein in the light quantity difference adjusting step, the light quantity difference is increased, by decreasing a light quantity of a light incident on one of the subject's eyes and maintaining a light quantity of a light incident on the other of the subject's eyes constant. 
 
     
     
       13. The eye-fatigue examining method according to  claim 9 , comprising
 arranging a transmitting area which can adjust a transmittance of a light, on an optical path of the light incident on at least one of the subject's eyes, 
 wherein, in the light quantity difference adjusting step, the light quantity difference is increased by adjusting the transmittance of the transmitting area. 
 
     
     
       14. The eye-fatigue examining method according to  claim 13 ,
 wherein when the transmitting area is arranged on an optical path of the light incident on each of the subject's eyes, the specific light quantity difference decided in the light quantity difference deciding step is expressed as a difference in the transmittance between the two transmitting areas. 
 
     
     
       15. The eye-fatigue examining method according to  claim 9 ,
 wherein in the light quantity difference adjusting step, the light quantity difference is continuously or stepwise increased. 
 
     
     
       16. The eye-fatigue examining method according to  claim 9 ,
 wherein the lights incident on the subject's eyes include a light in a first wavelength band and a light in a second wavelength band different from the first wavelength band, 
 a dichroic mirror is arranged on optical paths of the lights reflected by the subject's eyes, the dichroic mirror configured to transmit the light in the first wavelength band and reflect the light in the second wavelength band reflected by the subject's eyes to a side of the optical paths, and 
 in the gaze direction detecting step, the gaze directions are detected based on a result of detecting the light in the second wavelength band reflected by the dichroic mirror.